Light-weight FeCo/CNTs/HNTs triple-phase magnetic composites for high-performance microwave absorption

The preparation of lightweight, as well as high-performance microwave absorption materials, has attracted much attention in recent years, but people are still suffering from the high cost and low yielding of the products. Here a HNTs@CNTs (HCS) microsphere was prepared by spray drying, and then surface assembly of CoFe2O4 via the hydrothermal method to form HCS/CoFe2O4 composite, followed by thermal reduction into HCS/FeCo under H2/Ar atmosphere. The HCS/FeCo show significant performance in both permittivity and permeability due to the combination of the large magnetic moment of the FeCo alloy and the high conductivity of carbon nanotubes, leading to a remarkable enhancement in microwave absorption properties. Thanks to the unique morphology and the synergistic effect of multiple loss mechanisms, the maximum reflection loss of HCS /FeCo reached − 57.77 dB at 12.10 GHz with a matching thickness of only 1.63 mm, and the absorption bandwidth with reflection loss exceeding − 10 dB reached 6.24 GHz (11.76–18.00 GHz), which can completely cover the Ku band. In this strategy, the lightweight halloysite nanotubes are used to match the impedance parameters of the composite, and the spray drying method will facilitate the industrialization of the material.